The invention relates to an electromagnetic inductor and transformer device with at least 2 helical windings formed by planar technique into a coil as well as a core which amplifies an effect of the magnetic field lines created inside the adjacent windings of the coil.
High power transformer units typically include several coils and a metallic core, for example, a ferromagnetic or ferrimagnetic core, which magnetically couples the coils. The common alternating magnetic field can transform the voltage from a grid with one particular AC voltage to a different grid with a different AC voltage. Different types of coils and coil-shaped elements for such electrical or inductive components are known in the art.
For example, GB-A-2 260 222 discloses a coil made of a plurality of flat conductors that are arranged in a planar configuration. The flat conductors which are arranged side-by-side are connected at the center or inside of the coil by spot welding. To provide a sufficient large contact area for spot welding, the conductor ends project far into the coil center which considerably degrades the electrical efficiency.
Gaps can open and deposits can form at the connection points between several conductors which can aggravate corrosion. Moreover, inwardly projecting conductor ends affect the installation conditions. This results in performance limitations which will be described in detail hereinafter.
Coil bodies for wire-wound induction coils as well as planar transformers are designed for various efficiency and installation conditions, depending on the application. Conventional inductive elements can satisfy to some degree certain common requirements, in spite of the different applications:
a)Overall Size
The starting and end pieces that are formed when the coils are wound are typically connected to the outside. The overall size of multi-layer coils can be unnecessarily increased by cross connections (see U.S. Pat. No. 5,355,301; 4,873,757; 5,027,255; and 4,547,961).
b)Uniform Conductor Cross-section
The coils of planar transformers are formed of individual flat windings which are connected to each other by contacts. This produces joints which are subject to corrosion. Moreover, high currents can produce open circuits and arcing.
c)Electrical Efficiency
It is known that sharp corners and edgesxe2x80x94such as those occurring in cross connections in coilsxe2x80x94negatively affect the electric field lines. This causes a superposition and attenuation of the electric field and a degradation of the electric flux.
These electric field perturbations that can also negatively affect or interfere with surrounding components.
It would therefore be desirable to improve the cross-sectional efficiency of electro-magnetic inductor and transformer devices and to increase the power density by reducing the overall dimensions of the component, and more particularly, to achieve a uniform temperature distribution and to prevent hot spots.
It is further desirable that the new device can be used under high power without failure.
The invention is directed to an electromagnetic inductor and transformer device with at least two helical windings formed by planar technique to a coil as well as a core which amplifies an effect of the magnetic field lines created inside the adjacent windings of the coil.
According to one aspect of the invention an inductor and transformer device is characterized in that the coil having a starting section A and an end section E consists of one continuously formed conductor wound alternatingly from an inside to an outside of the interior space of the planar inductor and transformer device and vice versa to produce a microscopic homogeneous coil winding with corresponding magnetic field lines and wherein the core is divided by at least one dividing plane extending substantially parallel to the magnetic field lines with a cooling zone disposed in said parallel dividing plane which cooling zone for the purpose of heat removal extends from the interior space of the inductor and transformer device to the outside.
According to another aspect of the invention the inductor and transformer device includes a core that amplifies the effect of a magnetic field, wherein the core is divided into at least two core sections along planes that extend essentially parallel to the magnetic field in the core. At least one cooling gap is disposed between the core sections and oriented substantially parallel to a plane dividing the core sections. The cooling gap extends to an area located outside the core so that heat can be removed from the interior of the inductor and transformer device.
Its has been observed that heat can be removed more efficiently from the interior of the inductor and transformer device by dividing the core parallel to the magnetic flux lines. Hot spot can be eliminated by cooling the heated region of the divided core with a coolant fluid. Several cooling gaps can be formed in the region of the divided core, wherein the temperature between the cooler and the hotter regions can be evened out by convection cooling and/or by providing a strong coolant flow.
Embodiments of the invention may include one or more of the following features.
The core sections can be made of a ferrimagnetic or ferromagnetic material and the width of the cooling gap can be adjustable. A cooling element, which can include a cooling finger, can be provided for insertion in the cooling gap. The cooling element or cooling finger can be made of a non-magnetic materials with a high thermal conductivity, such as aluminum, an aluminum alloy or another light metal alloy. The core sections can be E-shaped and arranged in an opposing relationship, and one or more cooling gaps can be placed in the plane dividing the central yoke portion.
Further features and advantages of the present invention will be apparent from the following description of preferred embodiments and from the claims.